1. Field of the Invention
The present invention relates to a gas ring of an etching facility, and more particularly to a gas ring with curved surface on the edge of the gas-guiding trench thereof.
2. Description of the Prior Art
Etching technologies in the modem semiconductor industry primarily consist of wet etching and dry etching, wherein the dry etching usually includes physical type etching and chemical type etching. Specifically, the chemical type etching, also referred to as plasma etching, utilizes plasma to ionize the etch gas, thus generating ions, atoms, and radicals. Subsequently, the generated radicals react with the surface of the wafer under etch. In order to increase the plasma density, a magnetic field is introduced into the etch chamber in the modern magnetic-enhanced reactive ion etcher (MERIE). Moreover, for the purpose of reducing ion bombarding damage and increasing etching uniformity while maintaining high plasma density, another etch facility called transformer coupled plasma (TCP) is provided.
In a conventional etch facility, such as an etch equipment modeled LAM TCP 9400, etch gas such as Cl.sub.2 and HCl are conducted into a gas ring located on the bottom of the etch chamber, and are then guided through gas holes, finally entering into the chamber for reaction.
FIG. 1A shows a cross-sectional view illustrative of a portion of a conventional gas ring, and a magnified view around the corner of a gas-guiding trench is shown in FIG. 1B. As shown in the figure, the gas ring 10, which is mainly composed of metal Al, is usually covered with an Aluminum oxide layer 20 for protection, so that its erosion and resultant containment can be prevented. Unfortunately, the thickness of the Aluminum oxide layer 20 around the corner 10a of the gas ring 10 (FIG. 1B) is usually too thin to act as a blocking layer, thereby resulting in severe erosion and containment.
For the foregoing reasons, there is a need for a gas ring apparatus for semiconductor etching, so that erosion can be substantially reduced, and the maintenance cost can be lowered.